Voltage regulating transformer



y I946- A. H. B. WALKER 2,444,715 VOLTAGE aaeumwiue Tmsronm Filed Sept. 5, 1946 1m ATTORNEY VOLTAGE REGULATING TRANSFORMER Alec Hervey Bennett Walker, Ilondon, England, assignor, by mesne assignments, to'The Union 7 Switch and Signal Company, Swissvale, Pa., a

corporation of Pennsylvania Application September 5, 1946, Serial No. 695,028

In Great Britain August 17, 1945 4 Claims. (Cl. 323-56) This invention relates to voltage regulating apparatus'for alternating electric current circuits adapted to ensure the maintenance of a substantially constant voltage at the terminals of a load the outer legs 2. l of the core.

The leg 2 of the core is operated at a normal flux density, while the leg I is arranged to be operated at a relatively high flux density which is above the knee of the BH curve of the core circuit supplied with current from an alternat- 5 material. The output voltage is due principally ing current supply circuit regardless of variations to Winding 6, and this is reduced by windin 9 in the load and in the supply circuit voltage. sufiicientiy to stabilize the voltage across the out- A form of regulating apparatus of this charput terminals l2. The condenser l0 draws aleadacter devised by me is shown and described in mg curren in oppos ion to he m gn izing cur- British Patent No. 548,526, and comprises two 10 rent in winding 6 to provide the stabilizing action. transformers one of which is a two-coil trans- The winding of inductance II, which is in series former, the other having a'magnetlc core arwith condenser I0, is preferably mounted on a ranged to be operated ata relatively high flux ma netic core havin an air gap and rra ed density above the knee of the 8-H curve of the to oper e at a r l iv ly low flux density. core material, the primary windings of the transe Conde r a t 0 being conformers being connected in series with on annected in series across the output terminals,'conother across the alternating current supply clrstitute a filter circuit having a double action. In cult while the secondary windings are connected th first plac il H nd conde er II are so in series opposition with one another and in parchosen that at the supply frequency the filter allel with a series connected condenser and incircuit behaves as a condenser and draws a leadductances across the load circuit. ing current in opposition to the magnetizing cur- The present invention has for its object to prore t in Wi d 5 o provide the stabilizing ct o 'vlde novel and improved voltage regulating apwhile at the frequency of the third harmonic of Daratus of the same general character in which the supply req n y, wh h i the p p l the two transformers are combined into a single pon nt of the Wave form distortion, coil H and transformer comprising a core having partially condenser ID are in series resonance and appear separate magnetic flux paths, one of which 1 0pas a low resistance, therefore providing a virtual erated at thelrelatively high degree of satura- S or c it t t third harmonic magnetizing tion. current in winding '6. Owing to the purity of .One advantage of this combined arrangement w v m which results fr m t filter, t ciris that the portion of the core operated at the 0111i? y be y d y v c or d s as e lower'd'egree of magnetic saturation is available pl in e British p t e e n efore refor dissipating the heat developed in other por-' ferred to, wherein it is shown that a substantially tions of the core, another advantage being that co stant output voltage s a ta ed Wi Varying the windings may be so arranged and connected load and varyin input voltage. that the output voltage applied to the load cir- It will be evident that the form of apparatus cuitcan be arranged to have any desired value shown in Fig. 1 of the present application iselecrelative to the supply circuit voltage in a simple trically and. magnetically equivalent to that Of and convenient manner. the earlier form of apparatus above referred to. 7 The invention is illustrated byway of example 40 Referring now to Figure 2 in th o of in the accompanying drawings, Figures 1, 2, 3 apparatus a single primary winding H on the and 4 of which are diagrammatic views of difcentral leg l3 of the core I is connected to the ferent forms of regulating apparatus embodying pp y ui terminals an S on ary wind- 7 the invention. ings l5, l6 on-the outer legs 2, 1 respectively are Referring first to Figure 1 it will be seen that connected in series opposition to the load circuit this form of apparatus comprises a single threeterminals l2 in parallel with the series connected legged magnetic core I, an outer leg 2 of which condenser l0 and inductance II. The outer leg 2 is provided with a suitable air-gap 3. The leg of the core I is provided with a suitable air-gap 3 2 of the core is provided with awinding 4 conand the operation of this form of apparatus is nected in series with a portion 5 of a winding substantially; the same as h of the Prev ly ,6 on the other outer leg 1 across the supply cirknown apparatus above referred to. It will be cuit terminals 8. A winding 9 on the outer leg appreciated, however, that the primary winding 2 is connected in series opposition with the whole It is electrically separated from the secondary of the winding 6 on the outer leg l of the core windings l5, l6 which is of advantage in certain and in parallel with a series connected condenser applications of my invention. l0 and inductance l 1 across the; load circuit ter- Referring now to Figure 3 in this form of appaminals l2. The central leg l3 of the core I is ratus the-air-gap 3 is provided in the central leg not provided with any winding and serves to coml3 of the magnetic core I, the primary winding plete the path for the magnetic fluxes traversing it connected to the supply circuit terminals 8 being arranged on the portion of the core circuit including the outer leg 2. A secondary winding II on'the central leg l3 and a secondary winding it arranged as shown are connected in series opposition across the load circuit terminals l2 in parallel with the series-connected condenser l0 and inductance I I.

Referring now to Figure 4 a modified form of the apparatus of Figure 3 is shown in which the series-connected condenser l0 and inductance ll instead of being directly connected across the load circuit terminals are connected to separate windings I9, 20 on the same legs l3, 1 of the core as the secondary windings I1, I! this arrangement having the advantage that since the secondary windings l1, I! are entirely electrically separate from the primary winding i4 and from the condenser and inductance circuit, the voltage applied to the load circuit terminals I2 can be readily adapted to any particular requirements without interfering with the design of the rest of the apparatus.

Having now described my invention, what I claim as new and desire to secure by Letters Patent is:

1. Voltage regulating apparatus for an alternating current circuit of the kind described, in which a single transformer is provided comprising a primary winding on a magnetic core having partially separate magnetic flux paths one of which is operated at a relatively high flux density suillcient to cause wave form distortion and the other is operated at a low flux density, said apparatus comprising a main secondary winding on that portion of the magnetic core operated at a high flux density, a compensating winding connected in series opposition to said main winding on that portion of the magnetic core operated at a low flux density, and a filter comprising an inductance and a condenser tuned to series resonance at the third harmonic frequency of said alternating current eiiectively connected across said windings, the proportions of said filter being such that at the fundamental fl'u" quency of said alternating current said filter acts as a tuning condenser for said main winding of such a value that the current through said filter cooperating with the magnetizing current in said main winding serves to stabilize the voltage delivered by said apparatus.

2. Voltage regulating apparatus adapted to be interposed between the input and output terminals of an alternating current circuit comprising a transformer having a primary winding on a magnetic core with partially separate magnetic flux paths, a main secondary winding on a portion of said magnetic core operated at a high flux density sufficient to cause wave form distortion, a compensating winding on another portion of said magnetic core operated at a low flux density, said primary winding being connected in series with a portion at least of said main winding across said input terminals and said compensating winding being connected in series opposition with said main winding across said output terminals, and a filter comprising an inductance and a condenser tuned to series resonance at the principal harmonic frequency due to said wave form distortion connected across said output terminals, the proportions of said filter being such that it acts as a tuning condenser at the fundamental frequency .of said current and supplies magnetizing current to said main winding of a value sufficient to stabilize the voltage delivered to said output terminals.

3. Voltage regulating apparatus adapted to be interposed between the input and output terminals of an alternating current circuit comprising a transformer having a magnetic core with partially separate flux paths, a main secondary winding on a portion of its magnetic core operated at a high flux density suincient to cause wave form distortion, and a compensating winding on another portion of its magnetic core operated at a low flux density, said compensating winding being connected in series opposition with said main winding across said output terminals, a primary winding on said magnetic core for supplying flux to both said portions, said primary winding being connected across said input terminals, a filter comprising an inductance and a condenser connected in series across said output terminals and tuned to resonance at the principal harmonic frequency of said wave form distortion, said filter acting primarily as a tuning condenser at the fundamental frequency of said alternating current to supply magnetizing current to said windings for stabilizing the resultant voltage across said output terminals,

4. Voltage regulating apparatus adapted to be interposed in an alternating current circuit supplied with a varying primary voltage comprising a primary winding on a. magnetic core having two portions one of which includes an air gap for increasing its reluctance the other being of relatively low reluctance, a main winding on the low reluctance portion of said core for delivering induced secondary voltage, a condenser effectively connected in parallel with said main winding for tuning it to at least partial resonance whereby said low reluctance path is normally operated at a flux density approaching saturation thereby limiting the variation in the secondary voltage as the primary voltage varies and also causing distortion of the wave form, a compensating winding connected in series opposition to said main winding but mounted on the high reluctance portion of said core, said compensating winding supplying an opposing undistorted voltage which varies with the primary voltage so as to stabilize the fundamental component of the secondary voltage, an inductanc comprising an additional winding on a separate core connected in series with said condenser across said main and compensating windings, said additional winding serving to tune said condenser to series resonance to provide an effective short circuit for the principal harmonic component of said distorted wave form, whereby said secondary voltage is caused to have not only a substantially constant value but also a substantially undistorted wave form.

ALEC HERVEY BENNETT WALKER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,659,706 Rudenberg Feb. 21, 1928 2,313,440 Huge Mar. 9, 1943 2,364,558 Stocker Dec. 5, 1944 FOREIGN PATENTS Number Country Date 463,947 Great Britain Apr. 5, 1937 

